Proximity sensor using partial-transmissive-partial-reflective optical element with a same light transmission window and manufacturing method thereof

ABSTRACT

A proximity sensing device includes: a light source, a sensing unit, a light guide unit, and a window. The light source emits light, which is guided by the light guide unit to the window. The emitted light reflected by an object is received by the same window. The light guide unit includes a partial-transmissive-partial-reflective (PTPR) optical element, whereby the light emitted from the light source is reflected by the PTPR optical element, while the light reflected by the object passes through the PTPR optical element. There is only one window required.

CROSS REFERENCE

The present invention is a continuation of a co-pending application ofU.S. Ser. No. 16/745,483 filed on Jan. 17, 2020, which is a continuationof a co-pending application of U.S. Ser. No. 15/458,941 filed on Mar.14, 2017, which is a continuation-in-part application of U.S. Ser. No.15/226,599 filed on Aug. 2, 2016, which is a continuation application ofU.S. Ser. No. 14/061,709 filed on Oct. 23, 2013.

BACKGROUND OF THE INVENTION Field of Invention

The present invention relates to a proximity sensing device, especiallya proximity sensor including a light guide unit which includes apartial-transmissive-partial-reflective (PTPR) optical element such thatlight emitted from a light source and light reflected from an objectpass through the same window to reduce the area required for the window.

Description of Related Art

Proximity sensing devices are commonly employed in current handhelddevices. On the housing of the handheld device, a conventional proximitysensing device requires two separate windows, one for emitting a lightbeam to outside of the device and the other for receiving lightreflected from an outside object. In some design the two separatewindows are shown to be one slot-shaped area on the outer appearance ofthe handheld device, but actually it includes two separate lightpassages. The total size of the two separate windows or the slot-shapedarea is about 2.2-4 mm in its longer dimension. Apparently, this isdisadvantageous in terms of minimizing the size providing flexibility inappearance design of a handheld device.

SUMMARY OF THE INVENTION

In one perspective, the present invention provides a proximity sensingdevice, which includes: a light source, configured to operably emit alight beam for sensing a proximal status of an object; a sensing unit,configured to operably receive light reflected from the object, fordetermining the proximal status of the object; a light guide unit whichincludes a partial-transmissive-partial-reflective (PTPR) opticalelement, the PTPR optical element being configured to reflect at leastpart of the light beam emitted by the light source and transmit at leastpart of the light reflected from the object; and a window locatedbetween the light guide unit and the object, the same window beingconfigured to pass the light reflected by the light guide unit to theobject and pass the light reflected from the object to the light guideunit.

In one embodiment, the light source and the sensing unit are located ona same substrate, and the light guide unit further includes a reflectiveoptical element configured to reflect the light beam emitted by thelight source to the PTPR optical element, whereby the light beam emittedby the light source is first reflected by the reflective opticalelement, next reflected by the PTPR optical element, and further nextpassing through the window.

In one embodiment, a size of the window is not larger than 1 mm×1 mm.

In one embodiment, the proximity sensing device is located in a handhelddevice, which includes a transparent cover for covering the proximitysensing device, wherein the transparent cover includes an IR-ink(infrared ink) located at a location corresponding to the window.

In one embodiment, the PTPR optical element includes a transparent bodyand a semi-reflective surface on the transparent body.

In one embodiment, the semi-reflective surface includes a polarizationcoating.

In another perspective, the present invention provides a light guidingmethod of proximity sensing device, which includes steps of: emitting alight beam from inside a handheld device; reflecting the light beam, bya partial-transmissive-partial-reflective (PTPR) optical element, to awindow formed on the handheld device; receiving light from the samewindow; and guiding the received light to pass through the PTPR opticalelement, to a sensing device.

The objectives, technical details, features, and effects of the presentinvention will be better understood with regard to the detaileddescription of the embodiments below, with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a proximity sensing device according to one embodiment ofthe present invention.

FIG. 2 shows a PTPR optical element according to one embodiment of thepresent invention.

FIGS. 3A-3D show several embodiments of the enclosure, cover or housing,and the window.

FIG. 4 shows light paths for better comprehension.

FIG. 5 shows a light guiding method of proximity sensing deviceaccording to one embodiment of the present invention

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The drawings as referred to throughout the description of the presentinvention are for illustrative purpose only, o show the interrelationsbetween the components, but not drawn according to actual scale.

FIG. 1 shows a proximity sensing device 10 according to one embodimentof the present invention, for sensing a proximal status. The proximitysensing device 10 includes: a light source 11, a sensing unit 12, and alight guide unit 13. The proximity sensing device 10 emits and receiveslight through a same window 14. The window 14 can be regarded a part ofthe proximity sensing device 10, or if the proximity sensing device 10is employed in a handheld device, the window 14 for example can belocated on a housing of the handheld device.

The light source 11 and the sensing unit 12 are preferably located on asame substrate 1. The light source 11 is configured to operably providea light beam, for sensing a proximal status of an object (which isequivalent to sensing a proximal status of the proximity sensing device10 to the object). The sensing unit 12 is configured to operably receivelight reflected from the object, for determining the proximal status ofthe object. The light guide unit 13 guides the light beam emitted fromthe light source 11 to the window 14, and also guides the light receivedfrom the same window 14 to the sensing unit 12.

In one preferable embodiment, the light guide unit 13 includes apartial-transmissive-partial-reflective (PTPR) optical element 132,which is configured to reflect at least part of the light beam emittedby the light source and transmit at least part of the light reflectedfrom the object, whereby at least part of the light beam emitted by thelight source reaches the window and at least part of the light receivedfrom the window 14 reaches the sensing unit 12.

Referring to FIG. 2 , in one embodiment, the PTPR optical element 132includes a transparent body 1321 and a semi-reflective surface 1322located on the transparent body 1321. The semi-reflective surface 1322,in one embodiment, includes a polarization coating. The light beam fromthe light source 11 includes an s-polarized component and a p-polarizedcomponent. The polarization coating can reflect a certain portion of oneof the s-polarized component and p-polarized component, while it let acertain portion of the other of the s-polarized component andp-polarized component pass by. For example, the light source 11 can emitlight having a higher ratio of s-polarized component to p-polarizedcomponent, and the polarization coating is designed to reflect thes-polarized component but let go of the p-polarized component. The lightreflected by the object will not only include the emitted light but alsosome stray light, so if the object is close, there will be a significantamount of p-polarized component passing through the window 14, throughthe polarization coating and the transparent body 1321, to the sensingunit 12, as shown by the “received light” path.

Referring back to FIG. 1 , in one embodiment, the light guide unit 13further includes a reflective optical element 131, which is configuredto reflect the light beam emitted by the light source 11 to the PTPRoptical element 132, whereby the light beam emitted by the light source11 is first reflected by the reflective optical element 131, nextreflected by the PTPR optical element 132, and further next passingthrough the window 14.

The purpose to provide the reflective optical element 131 is to redirectthe light emitting direction, so that the light source 11 and thesensing unit 12 can be located on the same substrate 1, facing the samedirection. This helps to reduce the thickness of the proximity sensingdevice 10.

As per the reflective optical element 131, in one embodiment, thereflective optical element 131 can be a prism lens. In anotherembodiment, the reflective optical element 131 can be a mirror.

Referring to FIG. 1 , in one embodiment, the proximity sensing device 10itself may have an enclosure or cover 15, or when the proximity sensingdevice 10 is employed in a handheld device, the handheld device may havea housing 15. In one embodiment, the window 14 can be an opening in theenclosure or cover or housing 15.

FIGS. 3A-3D show several other embodiments. In FIG. 3A, the enclosure orcover or housing 15 is cover by a coating 16, at a locationcorresponding to the window. The coating 16 for example can be, but isnot limited to, a transparent coating, an IR-ink (infrared ink), or acoating capable of filtering a desired wavelength range. In FIG. 3B, thecoating 16 is inside the window. In FIG. 3C, another cover plate 17 isprovided on the enclosure or cover or housing 15, and the cover plate 17for example can be made of a substantially transparent material, or amaterial which is capable of filtering a desired wavelength range. Thecoating 16 is on the enclosure or cover or housing 15, while in thecover plate 17. In FIG. 3D, the coating 16 is inside the window.

FIG. 4 shows the light paths for emitting light outward and receivinglight inward. Because only one window is required for both the outwardlight path and the inward light path, the size of the area occupied bythe window is reduced. In one embodiment, the size of the window is notlarger than 1 mm×1 mm.

In one perspective, the present invention also provides a light guidingmethod of proximity sensing device. Pease refer to FIG. 5 , wherein thelight guiding method includes: emitting a light beam from inside ahandheld device (S1); reflecting the light beam, by a PTPR opticalelement, to a window formed on the handheld device (S2); receiving lightfrom the same window (S3); and guiding the received light to passthrough the PTPR optical element, to a sensing device (S4).

Note that, for illustration purpose, both the emitted light beam and thereceived light are represented by straight lines. However, according tonatural optical physics, the emitted light beam and the received lightin fact have light intensity distributions, and the drawings simplifyit. Therefore, in the context of the present invention, “light beam” or“light” does not require to be its complete intensity distribution, butcan be any significant portion thereof.

The present invention has been described in considerable detail withreference to certain preferred embodiments thereof. It should beunderstood that the description is for illustrative purpose, not forlimiting the scope of the present invention. Those skilled in this artcan readily conceive variations and modifications within the spirit ofthe present invention. Besides, an embodiment or a claim of the presentinvention does not need to attain or include all the objectives,advantages or features described in the above. The abstract and thetitle are provided for assisting searches and not to be read aslimitations to the scope of the present invention. It is not limited foreach of the embodiments described hereinbefore to be used alone; underthe spirit of the present invention, two or more of the embodimentsdescribed hereinbefore can be used in combination. For example, two ormore of the embodiments can be used together, or, a part of oneembodiment can be used to replace a corresponding part of anotherembodiment.

What is claimed is:
 1. An optical sensing device, comprising: a lightsource, configured to emit a light beam; a sensing unit, configured toreceive a reflected light beam; a light guide unit which includes apartial-transmissive-partial-reflective (PTPR) optical element, disposedin the transmission path of the light beam and the reflected light beam;and a window located between the PTPR optical element and the object,the light beam emitted from the light source and the reflected lightbeam passing through this same window; wherein the light source and thesensing unit are located on a same substrate, and the light beam emittedby the light source is first transmitted to the PTPR optical element,and further next is transmitted to pass through the window, wherein thereflected light passing through the window is transmitted to the PTPRoptical element, and further next is transmitted to the sensing unit. 2.The optical sensing device of claim 1, wherein a size of the window isnot larger than 1 mm×1 mm.
 3. The optical sensing device of claim 1,wherein the optical sensing device is located in a handheld device,which includes a transparent cover for covering the proximity sensingdevice, wherein the transparent cover includes an IR-ink (infrared ink)located at a location corresponding to the window.
 4. The opticalsensing device of claim 1, wherein the PTPR optical element includes atransparent body and a semi-reflective surface on the transparent body.5. The optical sensing device of claim 4, wherein the semi-reflectivesurface includes a polarization coating.